1. The Field of the Invention
The present invention relates generally to the attachment of a bone fixation assembly to a bone, and more particularly, to cerclage wiring and to systems and methods for implanting fixation systems to secure bone fragments together or to secure prostheses to bone.
2. The Relevant Technology
Cerclage wiring is a technique in which surgeons tie pieces of bone together using metal wire or cable. This is commonly done in trauma cases to repair fractures and can include a variety of bones and parts of bones including patella, olecranon, femur, trochanter, tibia, etc. In some cases cerclage wiring has also been using in hip replacements—if the patient has poor bone stock in the femur, the surgeon may insert the implant into the femur and then tie cables and plates to the bone as well to help support the implant and keep it from breaking out of the bone. This is common known as periprosthetic cerclage.
One difficult aspect of cerclage wiring is providing retensioning of the wire or cable. In some cases the cable is passed through a cable receiving element and the cable and/or the cable receiving element is crimped or deformed in some manner to prevent withdrawal of the cable through the element. Although this method can be effective it may create a loosening of the cable when crimping. In addition the cable and the cable receiving element are irreversibly deformed disallowing retightening or adjustment.
Other techniques include a button or a pin attachment of the cable to a cable receiving element. Again, these may cause permanent deformity of the cable disallowing retightening or adjustment.
Other systems may also have set screws that are not in line with the cable and when the screws are tightened against the system the screws press against the cable. This system along with many other designs causes damage or deformation of the cable.
With either of these techniques a larger incision may be required because of the need for multiple instruments to tension the cable and crimp the cable, the element or both. Furthermore the inability to retighten the cables may result in a greater number of cables being used and a greater amount of time for surgery.
As the above described techniques illustrate, the existing systems and procedures for cerclage wiring may not be as effective as desired.